Method of forming continuous structures of polytetrafluoroethylene

Claim 1

THE PROCESS WHICH COMPRISES COLD-DRAWING A COMPLETELY FUSED POLYTETRAFLUORETHYLENE TAPE 10 TO 50 PERCENT OF ITS UNDRAWN LENGTH, SNUGLY LAPPING THE DRAWN TAPE UPON AN ELONGATED HEAT-RESISTANT CORE OF GENERALLY CIRCULAR CROSS-SECTION TO FORM AN ASSEMBLY CONSISTING ESSENTIALLY OF SAID CORE AND A CONTINUOUS NON-INTEGRAL SHEATH OF SAID TAPE, IMMERSING SAID ASSEMBLY IN A CONVECTIVE HEATING MEDIUM AT A TEMPERATURE BELOW 300*C., INCREASING THE TEMPERATURE OF SAID MEDIUM TO 300*C., THENCE THROUGH THE 300* TO 327*C. RAGE AT A RATE NOT EXCEEDING 1.5*C. PER SECOND, TO A TEMPERATURE ABOVE 327*C., WHILE MAINTAINING SAID ASSEMBLY IMMERSED THEREIN, AND FURTHER HEATING SAID ASSEMBLY AT A TEMPERATURE ABOVE 327*C. UNTIL SAID SHEATH IS CONVERTED TO INTEGRAL FORM.